Generally, the structure of a fixing roller/fixing belt used in a copier and the like is such that a cylindrical substrate has a rubber layer formed as an elastic layer thereon, and a surface layer made of fluororesin such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) or polytetrafluoroethylene (PTFE) is formed on the elastic layer. Here, the fixing roller/fixing belt is a roller or a belt that is used for a fixing part in a copier. Examples of the process for manufacturing such a fixing roller/fixing belt are described in Patent Document 1. In the following explanation, PFA is adopted as an example of the fluororesin used for the surface layer.
That is, an adhesive is applied to the surface of the cylindrical substrate and the adhesive is bonded with a rubber layer (e.g., silicone-based rubber) formed thereon. Apart from this, PFA is applied onto the inner circumferential surface of a circular mold (a pipe), and after baking, the PFA is pulled out in a tubular form from the circular mold. The inner diameter of this tubular PFA is designed to be a little smaller than the outer diameter of the circular rubber layer. Moreover, in order to enhance the adhering strength relative to the below-described adhesive for a surface layer, the inner circumferential surface of the tubular PFA is treated (plasma treatment, chemical etching, or the like).
Next, the tubular PFA is radially expanded to increase the inner diameter, and it is compulsorily inserted over a cylindrical substrate having a rubber layer whose outer circumferential surface is previously coated with a surface-layer adhesive (silicone-based rubber). The surface-layer adhesive is comparatively thickly applied so that it may also function as a lubrication enabling the PFA to be smoothly inserted over the rubber layer. Thereafter, the circumferential surface of the tubular PFA is made flat and smooth by squeezing the surface of the tubular PFA to remove the excess of the surface-layer adhesive existing between the tubular PFA and the rubber layer and to remove wrinkles, sagging, etc. of the tubular PFA and voids which have occurred between the tubular PFA and the rubber layer when the tubular PFA is inserted over the cylindrical substrate. Further, a PFA layer is formed by bonding the inner circumferential surface of the tubular PFA to the outer circumferential surface of the rubber layer through the surface-layer adhesive by heating for a pre-determined time at a temperature of 220° C.
A technique for covering a fluororesin layer, which is to become a surface layer, on an elastic layer formed on a cylindrical substrate is described in Patent Document 2. The technique is such that the outside of the elastic layer and the fluororesin layer are covered with a heat-shrinkable tube that has been shrunk by heating, and thereafter the fluororesin layer is baked by heating so that the internal shape of the heat-shrinkable tube is transcribed to the surface of the fluororesin layer. In such case, the heat-shrinkable tube is removed after the inner shape thereof has been transcribed to the surface of the fluororesin layer.
The technique described in Patent Document 3 is such that a columnar body that has been treated in advance with a primer is covered with a heat-shrinkable tube made of fluororesin (PFA) and the heat-shrinkable tube is shrunk to be fixed at a temperature (80 to 250° C.) less than the melting point thereof and is heat-bonded at a temperature (330 to 400° C.) above the melting point.
[Patent Document 1] Japanese Patent Application Publication No. 2004-276290
[Patent Document 2] Japanese Patent Application Publication No. H10-142988
[Patent Document 3] Japanese Patent Application Publication No. S64-1534